The structural stability of a fragment containing the oligomerization domain of the tumor suppressor p53 has been studied using DSC and CD. Previous NMR solution structural determinations on a similar construct revealed that the fragment forms a symmetric tetramer composed of a dimer of dimers. Thermal unfolding of this tetramer was reversible and can be described as a two state transition in which the folded tetramer is converted directly to unfolded monomers. It is thought that the abridged version, in which the disordered ends have been clipped would have similar behavior.